Cell Biology: Small Molecules and Cellular Processes

Study Notes

Cellular Composition and Function

Small molecules, including water, account for 75-80% of living matter by weight and 75% of a cell's volume.
These small molecules serve as substrates for many cellular reactions, including energy metabolism and cell signaling.
Cells acquire small molecules through importation and synthesis within the cell.

Proteins

Proteins are the most abundant and functionally versatile cellular macromolecules.
Proteins are formed by stringing together 20 different amino acids in linear chains, with a defined sequence.
The linear chain of amino acids folds into a complex shape, conferring a distinctive three-dimensional structure and function on the protein.
Proteins have various functions in the cell, including:
- Enzymes that accelerate chemical reactions
- Structural components of the cell (cytoskeletal proteins)
- Sensors that change shape in response to changes in the cell
- Import and export of small molecules and ions (proteins embedded in the cell-surface membrane)
- Hormones and hormone receptors that regulate cell function
- Binding to specific segments of DNA to turn genes on or off

Nucleic Acids

Deoxyribonucleic acid (DNA) is the cell's "master molecule" that carries coded information for making proteins at the right time and place.
The three-dimensional structure of DNA is a double helix, first proposed by James D. Watson and Francis H.C. Crick in 1953.
DNA strands are composed of nucleotides, which are often referred to as bases because they contain cyclic organic bases.
Four different nucleotides (A, T, C, and G) are joined to form a DNA strand, with the base parts projecting inward from the backbone of the strand.
Specific segments of DNA, termed genes, carry instructions for making specific proteins.
Genes contain two parts: the coding region specifies the amino acid sequence of a protein, and the regulatory region controls when and in which cell the gene's protein is made.

Description

This quiz covers the role of small molecules, including water and organic compounds, in cellular processes such as energy metabolism and cell signaling. It explores their importance in molecular cell biology.